Ladle for inductive treatment

ABSTRACT

A ladle for inductive treatment, having a non-magnetic metal casing and a refractory lining, the metal casing being made up of a plurality of elements each forming an open circuit, each of small section relative to the inductive vector and each insulated from its neighbors.

, [72] Inventor:

United States Patent Babel [54] LADLE FOR INDUCTIVE TREATMENT LouisBabel, Sauvigny-les-Bois, France [73] Assignee: Creusot-Loire, Paris,France [22] Filed: April 7, 1971' [21] Appl.No.: 131,926

[30] Foreign Application Priority Data [4 Nov. 21, 1972 PrimaryExaminerJ. V. Truhe Assistant Examiner-B. A. Reynolds Attorney-Cameron,Kerkam & Sutton [52] U.S. c1 ..13/27, 219/1049 51 Int. Cl. ..H05b s/12 11 ABSTRACT [58] Fieldoi Search ..219/ 10.49, 10.79; 13/26, 27, A ladlefor inductive treatment, having a 13,32 5 netic metal casing and arefractory lining, the metal casing being made up of a plurality ofelements each [56] Reference-s cued forming an open circuit, each ofsmall section relative UNITED STATES PATENTS to theinductive vector andeach insulated from its nei bors. 2,969,411 1/196-1 Gibbs ..219/10.79 Xgh 3,401,227 9/1968 Dunlery et a1. ..13/26 X 1 Claim, 10 Drawing Figures"T A r ,Qpf l 'lTILCL.

PATENTED nuv 2 1 1972 SHEET 2 0F 5 FIG:'3

PATENTEU luv 2 I I972 SHEET UF 5 LOQQOOGOOOOQOOOOQOOO mum 1912 sum s or5 LADLE FOR INDUCTIVE TREATMENT This invention relates to a ladle forinductive treatments, more particularly for the treatment of metals andalloys in the molten state by means of very low, low andmedium-frequency inductive alternating fields (5 Hz to 2,500 I-Iz).

Ladles for inductive treatments are known, which consist of a refractorylining inside a non-magnetic metal cylindrical casing which, in theheating zone, is formed by an assembly of metal'elements connected bymortise and tenon joints and electrically insulated from one another byan insulating and refractory gasket consisting of a thermosetting cementinjected in the liquid state into continuous interstices between theconnected metal elements. An arrangement of this type has been describedmore particularly in French Patent No. 1,509,043.

If the ladle capacity decreases, the metal inside the ladle must beheated with frequencies above 60 cycles and as high as 2,500 cycles (10to 15 kg ladles). The

known ladles defined hereinabove have the disadvantage that they cannotbe used in practice when the frequency of the inductive current is above60 cycles. The reason for this is that with, higher frequencies theheating produced in the metal casing of the ladle as a result, moreparticularly, of eddy currents (eddy current losses proportional to thesquare of the frequenveryrapidly cause the ladle to become unusable.

The invention obviates this disadvantage and enables frequencies of ashigh as 2,500 Hz to be used with a ladle consisting of a cylindricalnon-magnetic metal casing which can receive a refractory lining.According to the invention, the metal casing consists of metal elementseach forming an open electrical circuit and each having a very smallsection in relation to the inductive vector, anelectrical insulatorbeing interposed between each element. I I

The invention will now be described in greater detail with reference toa number ofv specific embodiments given by way of example andillustrated in the drawings.

FIGS. 1 and 2 are a simplified view of one embodiment in which thecasing elements are radiating elements. FIG. 1 is a perspective view indiametric section and FIG. 2 is a top plan view.

FIGS. 3 and 4 show another embodiment with spirally wound metalelements. FIG. 3 is a diametric section of the metal casing of theladle. FIG. 4 is a section on IV-IV in FIG. 3.

FIG. 5 is a variant of the preceding embodiment in which the elementsare wound flat.

FIGS. 6, 7 and 8 relate to an embodiment in which the metal casingconsists of a braiding acting as a framework or reinforcement for therefractory concrete. FIG. 6 is a simplified perspective of the body ofsuch a ladle, FIG. 7 is a detail of the metal braiding and FIG. 8 is asection on the line VIIIVIII in FIG. 7.

FIG. 9 shows aladle according to the invention in position at aninductive heating station.

FIG. 10 illustrates possibilities for transporting the ladle and shows asystem providing protection during transport or pouring.

Referring to FIGS. 1 and 2, the metal casing of the ladle is formed byjuxtaposing a large number of identical elements 1. The shape of eachelement 1 is a radial section of the cylinder required to form the metalcasing of the ladle. In plan view as shown in FIG. 2, each element 1 isin the form of a very thin segment of adequate but very limited width.It will be seen that the juxtaposition of all the elements 1 forms thecylinder making up the ladle and its base. The elements are held inclamped engagement by hoops fitting in grooves 2 and 3 formed by thejuxtaposition of identical notches on all the elements 1. Theinterconnection of the elements 1 is completed by electrically insulatedfasteners 4 which connect the elements in groups of 4 or 5.

The elements 1 are made, for example, from a nonmagnetic alloy (nickelbase, cobalt, chromium, titanium and aluminum) i.e., a super refractoryprecipitation hardened alloy of high electrical resistivity. Eachelement is electrically insulated by a surface coating of chromiumoxide.

FIGS. 3 and 4 illustrate another embodiment of the metal casing of aladle which in this case consists of a circular-section wire 5 woundspirally after the style of a spring and held between two rings 6 and 7.The turns of the spring 5 are held in contiguous relationship by meansof a number of tie-rods 8 regularly distributed around the wall formedby the spring and alternately inside and outside said wall-.Clamping isprovided by nuts 9 with the interposition of resilient washers 10.

The spring 5 may consist of a single wire wound over the entireheight'of the ladle and preferably (no-load tension) by a plurality ofsuper-posed unit springs. The springs 5 and the tie-rods 8 may, forexample, be made from a super refractory alloy as defined hereinbefore.

The bottom non-magnetic ring 7 is made in two parts which are connectedby bolts. The ring 7 has an annular groove 11 to receive the matchingelements of juxtaposed rectilinear metal bands 12 which are held in thegroove 11 when the two parts of the ring 7 are connected. The bands 12are laminations made from nonmagnetic alloys, generally used forresistors. The assembly of elements formed by the turns of the spring 5,the tie-rods 8 and the metal bands 12 are electrically insulated by achromium oxide surface coating.

The structure shown in FIG. 5 is very substantially similar to thatshown in FIGS. 3 and 4 but the spiral winding in this case is replacedby a superimposition of flat circular rings 15 clamped in the same waybetween annular elements 6 and 7 by means of tie-rods 8 and nuts 9. Therings 15 are not continuous but are split rings. As in the previousFigures, they are of a super refractory alloy and are electricallyinsulated by a layer of chromium oxide.

Referring now to FIGS. 6, 7 and 8, the metal framework of the ladleconsists of a series of tie-rods 18 uniformly spaced and disposed alonggeneratrices of the cylinder forming the body of the ladle. The tie-rods18 are connected in pairs by a wire 19 wound as an open spiral aroundtwo consecutive tie-rods 18. The turns of each spiral 19 are interlacedwith the turns of the adjacent spirals, thus forming a resilientbraiding which is closed on itself in the form of a cylinder. Thetie-rods 18 and the spirals 19 are of a non-magnetic super refractoryalloy like the elements in the embodiment described hereinabove. Eachtie-rod 18 is enclosed by a sheath of silico-alumina fibers which forman insulator, while the spirals 19 are electrically insulated by achromium oxide coating.

The braiding consisting of the tie-rods l8 and the spirals 19 isembedded in a layer of refractory concrete 21. The concrete cylinder 21together with the metal braiding as a reinforcement will preferably beprestressed. For this purpose, the braiding will be disposed at theperiphery of an expansible mandrel and be tensioned, the system beingdisposed in a mold into which refractory concrete is then poured. Afterthe concrete has set and the expansible mandrel has been withdrawn, theresilient shrinkage of the braiding will provide the prestressing forthe concrete. 7

The resulting cylinder will then be completed by a base which can be ofthe type shown in the previous FIGS. 3, 4 and 5, and some of thetie-rods 18 will be longer than the others and their ends will projectbeyond the actual cylinder to enable the base to be fixed.

Of course the descriptions given concern only the metal casing of theladle, which in every case will receive a bottom refractory liningformed in conventional known manner.

In all the above-described embodiments, the metal elements forming themechanical resistant element of the ladle all have a very small sectionin relation to the induction vector and never form a closed electricalloop. The currents directly induced in the framework are thus zero andthe eddy currents are reduced to a minimum by reduction of the passagesection for the inductive flux in the metal parts forming the framework.Also, since the metal frameworks are non-magnetic they do not interferewith the action of the effective induction vector on the chargecontained in the ladle.

The advantage of a ladle of this kind constructed according to theinvention is that it provides, for example, a readily replaceabledetachable crucible for an induction furnace in which only the inductivewinding is a fixed element, and a furnace of this type can userelatively high current frequencies (up to 2,500 Hz) despite thepresence of a metal framework in the ladle. The use of such a ladle alsoenables elementary metallurgical sequences (vacuum melting,super-heating, holding) to be separated, by transferring the ladlesuccessively to fixed working stations each corresponding to aspecialization of the fixed induction equipment.

FIG. 9 is a simplified view of an induction furnace comprising a fixedinductive winding 25 disposed at the periphery of a tank 26. The latter,closed at the bottom by a base 27, is open at the top and is bounded bya collar 28 provided with a cooled gasket 29. The ladle used here is ofthe type described in FIG. 3, with a spiral framework 5 and tie-rods 8.It is lined on the inside by a refractory lining 30 and has in the basea taphole 31 with a valve-controlled nozzle 32. The top annular collar 6is connected to a projecting collar 33 provided with lifting lugs 34.When the ladle is in position in the tank 26, the collar 33 rests on thecollar 28 of the furnace. When the metallurgical operation is to becarried out in a vacuum or in a controlled atmosphere, the assembly canbe completed by a bell 35 resting on the collar 33 with theinterposition of a cooled gasket 36.

FIG. 10 shows equipment for transportation of the ladle from onetreatment station to another or for supporting the ladle during apouring operation. The equipment comprises 'a tank 35, on the edge ofwhich the top collar 6 of the ladle rests. If this equipment is used totilt the ladle, the latter is also connected to the about which theladle can be tilted for filling or emptying operations.

'Of course the invention is not limited solely to the embodimentsdescribed hereinbefore, but also covers other embodiments differingtherefrom only in detail. Thus the mechanical resistance of the ladlesshown in FIGS. 3 and 5 could be reinforced by a concrete lining asdescribed in connection with the framework in FIG. 7. The spirallywoundelements forming the framework of the ladle shown in FIG. 3 could betubular and form a peripheral cooling circuit for the ladle, suchcircuit being connected to an external fluid circulation circuit.

I claim:

1. A ladle for inductive treatments, consisting of a non-magneticcylindrical metal casing, a refractory lining for said casing, saidmetal casing consisting of metal elements each forming an openelectrical circuit and each having a very small section in relation tothe inductive vector, an electrical insulator interposed between each ofsaid elements, said metal elements including a first series ofrectilinear elements regularly disposed along generatrices of thecylinder, and a second series of elements wound spirally between twoconsecutive rectilinear elements, the turns of each spiral'interengaging between the turns of the adjacent spirals, a cylindricalwall of refractory concrete enclosing said series of elements, and metalelements forming the base of said casing being juxtaposed non-magneticelectrically insulated strips in a flat annular element and connected tothose of said rectilinear elements projecting beyond said cylindricalbody.

1. A ladle for inductive treatments, consisting of a nonmagneticcylindrical metal casing, a refractory lining for said casing, saidmetal casing consisting of metal elements each forming an openelectrical circuit and each having a very small section in relation tothe inductive vector, an electrical insulator interposed between each ofsaid elements, said metal elements including a first series ofrectilinear elements regularly disposed along generatrices of thecylinder, and a second series of elements wound spirally between twoconsecutive rectilinear elements, the turns of each spiral interengagingbetween the turns of the adjacent spirals, a cylindrical wall ofrefractory concrete enclosing said series of elements, and metalelements forming the base of said casing being juxtaposed nonmagneticelectrically insulated strips in a flat annular element and connected tothose of said rectilinear elements projecting beyond said cylindricalbody.